Yeah, github is important. And yes, github is a little confusing at first.
Git is the technology for managing different versions of your app. It is very powerful if you have a team working on the same app in different stages that need to be merged at various points and allow you to back up. It is truly amazing what it manages to do.
Github is a web service that gives you a place to store these repos (short for repositories) so different people can have access. There are other services, but github is common and free. On a most basic level, you can “push” up the current version of your code so you have a permanent storage. That’s mostly what you’ll do in the beginning.
Github has documentation and I’m sure there are videos on how to get started. If you want to get deeper, there is a free ebook out there called Mastering Git. It may too much for you at this point, but will help with a deeper understanding. Personally, I think that the more complicated parts of git are just too hard to understand until you’ve worked on a large project with lots of people. But you can get the basics.